Condensate removing apparatus



June 13,1954 J. P. DOBBINS CONDENSATE REMOVING APPARATUS 5 Sheets-Sheet1 Filed Nov. 19, 1949 INVENTOR. JOHN P. DOES/N5 BY %%114 Afik ATTORNEYJune 15, 1954 J. P. DOBBINS 2,681,409

CONDENSATE REMOVING APPARATUS Filed Nov. 19, 1949 5 Sheets-Sheet 2 IN VEN TOR. JOHN P. DOBB/NS ATTORNEY June 15, 1954 J. P. DOBBINS 2,681,409

CONDENSATE REMOVING APPARATUS Filed Nov. 19, 1949 3 Sheets-Sheet 3 F/GINVENTOR.

JOHN P. DOBB/NS ATTORNEY Patented June 15, 1954 CONDENSATE REMOVINGAPPARATUS John P. Dobbins, Los Angeles, Calif., assignor to NorthAmerican Aviation, Inc.

Application November 19, 1949, Serial No. 128,383

1 Claim. 1

This invention pertain to an arrangement for removing ice or otheraqueous condensates from various parts of vehicles such as aircraft, andfor preventing their collection or formation on such parts.

In the past attempts have been made to use radiant heat sources forthese purposes, but it has been found that the forms of apparatuspreviously used are incapable of supplying energy that will accomplishthe purpose. More particularly it has been found that the spectraldistribution of the radiation emitted by the systems used in the pastcorresponds with temperatures which are too low for adequate radianttransmission through filters used for obstructing visible light. Also,the output intensities of such systems are insumcient to meet the heatdelivery requirements for ice removal in severe weather conditions.

Efforts have been made to deice Windshields by the use of radiant-heaterapparatus constituting virtually a heater rather than apparatus thateffectively applies radiation in the infrared and near-visible rangeaccording to the present invention. Emitters such a Calrod heatingelements, manufactured by the General Electric Company, or Chromaloxrods, manufactured by the Montgomery Bros. Manufacturing Company, havebeen proposed for such use but have been found to be unsatisfactory forthe reason that an open face heater of a size which can be used withaircraft Windshields cannot deliver sufiicient heat at the front surfaceof the receiving panel under known flight conditions to provide from1,000 to 2,000 B. t. u. per square foot per hour, without giving offradiation in the visible range. Any attempt to filter out visible lightin an arrangement such as this by means of ruby glass resulted in eithera heating source which was too large and cumbersome to be included inaircraft cockpits, or did not have suificient energy output to obtainthe intended purpose. A compact source that will accomplish the intendedpurpose is referred to herein as a high-intensity source.

It has also been proposed, prior to this invention, to provide a surfacewith an electrically conductive coating for delivery of deicing heat.This arrangement has not proved satisfactory for several reasons, andparticularly because of difficulties encountered in supplying heatuniformly to curved or non-rectangular shaped areas such as are commonlyencountered in aircraft windshields.

Applicant has solved the problem of obtaining sumcient radiation tomeetthe deicing requirements by the use of an incandescent lamp of specialconstruction which emits a preponderance of radiation in the nearvisible range to thereby provide a compact unit such as can be includedin an aircraft cockpit, but at the same time one which willsatisfactorily obtain the desired deicing results. Such a lamp isparticularly usable with a novel filter arrangement which readilytransmits long-wave and near-visible radiation but which filters outvisible radiation. This filter may also be used with bare wire orrod-type heating elements in small compact sizes to accomplish thepurpose of the invention.

Accordingly, it is an object of this invention to provide an arrangementwhich can be located in the interior of an insulating structure butwhich will satisfactorily deice the exterior of such structure.

t is a further object of this invention to provide a windshield deicingarrangement which utilizes short, high-intensity waves, but which is notaccompanied by visible light such as would be objectionable in anaircraft cockpit.

It is yet another object of this invention to provide a method ofheating transparent and diathermanous panels on aircraft to preventcollection of ice thereon and to remove ice or fog formations therefrom.

It is still another object of this invention to provide an arrangementwhich will satisfactorily deice radomes of radar units withoutinterfering with the operation of the radar.

It is still another object of this invention to provide a new and novelarrangement for emitting radiant energy that will satisfactorily deicewindshields and yet not provide visible light.

Other objects of invention will become apparent from the followingdescription taken in connection with the accompanying drawings, in which-Fig. 1 is a perspective View of an airplane involving the invention;

Fig. 2 is a sectional View, through the windshield, of the invention;

Fig. 3 is a cross-sectional view through a lamp arrangement forming partof the invention;

Fig. 4 is a sectional view of the lamp, reflector, and filter assembly,illustrated in Fig. 3;

Fig. 5 is a cross-sectional view of a modified form of radiant heatsource;

Fig. 6 is a sectional view through a radome unit in which the inventionis incorporated;

Figs. 7, 8, and 9 are sectional views of modified lamp arrangements;

Fig. 10 is a sectional view along lines l0--i0 of Figs. 7, 8, and 9; and

Fig. 11 is a cross-sectional view through a lamp having a modifiedreflector arrangement.

Referring to the drawings, Fig. 1 represents an airplane, such as anight fighter, equipped with a windshield 2, and a radome unit 3 forenclosing radar equipment, to which the invention may be applied.

Referring generally to Fig. 2 there is illustrated a windshield elementsuitably carried by frame and with which is associated heat source 6.Each of these heat sources is formed of a reflector T in which ismounted a lamp 8 of incandescent types comprising a transparent quartzenvelope filled with inert gas and in which is located a suitablefilament 9. Associated with the reflector 1 is a filter member it ofruby glass or the like for filtering out any visible light transmittedthrough the quartz glass 8. The ruby glass is used in sections ofapproximately 3 5 thick and in one form is known as the No. 2540 Corninginfrared filter. The beam spread of the lamp is illustrated by dottedlines.

This combination provides a satisfactory deicing arrangement wherein thehigh temperature of the lamp results in the production of long and shortwave-lengths, most of which pass through the ruby glass. However, sinceruby glass transmits radiation in the near-visible range, it isparticularly adaptable for use with a lamp source. It does not, however,transmit radiation in the visible range or in the infrared range beyondabout five microns. The quartz glass of the lamp is highly desirablebecause, compared with other glass compositions, it is more transmissiveof long-wave radiation. Further, the quartz glass withstands highertemperatures than other forms of vitreous material used for thispurpose. Since visible light is of shorter wave-length than one micron,and varies from approximately 0.4 to 0.8 of a micron, short-waveradiation, in the sense used in this disclosure, refers to that whichhas a wave-length of less than approximately one micron, whereaslong-wave radiation is that which has a wave-length greater than approxhmately one micron.

In a modified form of the invention, as shown in Fig. 5,. a filament His associated with a refiector l2 and a filter l3 of crystalline silverchloride. The filter is formed by cooling down slowly a mass of moltensilver chloride to produce a single crystal. This results in arelatively large crystal from which sheets may be out which are passedthrough metal rolls. The resulting sheets of material may be dipped inan alkaline-sulfide bath, thereupon producing a shiny black surface ofsilver sulfide (AgzS) in accordance with the technique disclosed in theJournal of the Optical Company of America, volume 37, No. 5, page 340,May, 1 -17, by Dr. H. C. Kremers, in which the sheet is coated for thepurpose of protecting the sheet from damage which may be occasioned bythe passage therelnto of ultra-violet and short-wave visible light. Thisparticular subject matter is also disclosed in U. S. Patents No.2,l20,955 and No. 2,420,956, issued May 20, 1947 to Harry C. Kremers.The sheet material may be dipped and rerolled until it is opacified to asatisfactory degree or to a degree wherein visible light will befiltered out to where less than one percent passes there through. Thetransmitted infrared rays, however, are not appreciably diminished in.intensity by the coating. This arrangement is highly chicient for thereason that the visible portion of the spectrum is selectively reflectedand absorbed by the coating on the sheet, whereas wave-lengths in theinfrared and near-visible range are transmitted. Light does notphotochemically affect the silver chloride when the latter is coatedwith silver sulfide and, accordingly, the material will not darken whenused or exposed to light for long periods of time. Multiple-crystalsilver chloride may be used instead of the single-crystal form, althoughit is not quite so efficient in the transmission of the long-waveradiation.

Other materials than silver chloride will function satisfactorily forthe intended purpose, these including other halides of silver as well asthose of lead, gold, or other suitable heavy-metal salts capable oftransmitting long-wave radiation. Desirable characteristics of suchmaterials are that they have good forming, weathering, temperature, andstability characteristics. The material also must be capable of beingcoated readily so as to prevent transmission of visible radiation. Inaddition to the sulfides coated on the halide bases, selenides andtellurides may be used on such bases, or metallic selenium may bedeposited as a thin film on the surfaces of the sheets for preventingtransmission of visible radiation. Gilsonite coatings, or evenelementary sulfur or tellurium may also be used in lieu of selenium.

Referring now to the arrangement in Fig. 6, a high-intensity radiantsource 21 of either the external reflector type units illustrated inFigs. 3-5, or the internal reflector type units illustrated in Figs.7-11, but circular in shape, is placed at the circumference of a radarscanning unit l5. This arrangement avoids any interference with theoperation of the radar scanning unit while at the same time effectivelydeices the radome structure i6. If desired, the radar scanning unititself may be the emitter of thermal radiation to the radome unit. Heatsupplied to the scanning unit may be in the form of electrical energydissipated through resistance units.

Referring to Figs. '7, 8, 9, l0, and 11, there are illustrated lamps ofthe incandescent type having glass portion ll, filament iii, reflectorl9, end supports 2%), and supporting disks 2|. Rod members 22 and 22aare slidably supported in disk members 2! and adapted to be connected tosupports 20 by Wire elements 23 or the like. Filament It may besupported by wire 28 and projection 29 as typically illustrated in Figs.'7 and 10. Conductor elements 24 are adapted to be connected to asuitable source of power. In the arrangement illustrated in Fig. 7 theconductor elements 24 are on opposite sides and ends of the tube,whereas in Fig. 8 conductor elements 24 are on the same end. In Fig. 9the conductor elements 24 are on opposite sides of the tube but thefilament i8 is supported at one end by a conducting member 14 carried bytwo of bars 22 but out of contact, and at the other end by spring member25. An additional reflector 25 may be used as illustrated in Fig. 11 ifdesired to limit the angular divergence of the beam.

In one form of construction, to solve the requirements of a particularairplane, it has been discovered that the envelope of the lamp is formedof glass tubing fabricated from Corning No. 2560 series material, usingparticularly No. 2562 glass which has an annealing point of 565 C. and astrain point of 531 C. A wall thickness of about a -inch has been foundto be satisfactory. The inside surface of the envelope is coated over anangle of approximately 210? of are along a length of about 25 incheswith metallie silver or gold. This construction obtains an operatingtemperature of the front glass surface of 500 C. and a temperature onthe rear surface of approximately 450 C. The envelope contains a gascomposed of approximately 95% argon or krypton-the balance, nitrogen.During full-power operation an internal gas pressure of approximately450 mm. of mercury is obtained. A filament of drawn tungsten wire isused and is located approximately 0.17 inch from the reflec tor surface,and symmetrically disposed thereto. The heating element comprises asingle 25-inch coil filament wound at A;-inch average diameter to give220 total turns. The diameter of the filament is approximately 1.35 mm.and 220 cm. in length. The over-all length of this lamp will beapproximately 30 inches, With a diameter of about one inch, and willoperate at 28 volts with an input of about 1,000 watts. This willsatisfactorily deice an area of windshield approximately 8 in. x 30 in.

A lamp source of radiant energy for purposes of the invention is moreeffective, when used for heating plastic Windshields or enclosures, thanthe low-temperature open wire type source, for the reason that theshorter wavelengths emitted by the lamp are better transmitted throughthe plastic material to heat it throughout, together with any condensatewhich may appear on the exterior thereof; whereas the low-temperaturetype, emitting long-wave radiation, must necessarily heat the nearsurface of the material, which material is then heated throughout itsthickness by conduction. This would require a greater amount of energyto accomplish the desired objective with thick sheets, and isaccompanied by a greater danger of cracking the glass when used to deicethat type of windshield.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample only and is not to be taken by way of limitation, the spiritand. scope of this invention being limited only by the terms of the appended claim.

I claim:

A device for de-icing the remote side of a nonmetallic panel comprisingan elongated hightemperature short wave infrared radiation-pro ducingfilament; an elongated sealed quartz glass tubular envelope having anon-oxidizing interior atmosphere disposed in surrounding relationshipwith said filament for transmitting the radiation produced thereby;means disposed between said envelope and a non-metallic panel forfiltering the visible spectral components from said radiation; and meansclosely associated with said envelope for reflecting said radiationthrough said filter means and against said panel, whereby said radiationpasses through said panel for re moving ice and condensate on thesurface thereof remote from said device.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,032,267 Bastian July 9, 1912 1,852,599 Zaiger et a1. Apr. 5,1932 1,917,141 Middleton July 4, 1933 2,317,019 Altemus Apr. 20, 19432,319,912 Anderson et a1 May 25, 1943 2,375,369 Knight et al May 8, 19452,408,867 McCollum Oct. 8, 1946 2,414,520 Greenwald nnnnnn Jan. 21, 19472,424,454 Gordon July 22, 1947 2,438,972 Hoffman Apr. 6, 1948

